Jiang Jian, Gao Yurui, Zhu Weiduo, Liu Yuan, Zhu Chongqin, Francisco Joseph S, Zeng Xiao Cheng
Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States.
Laboratory of Theoretical and Computational Nanoscience and Technology, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
J Am Chem Soc. 2021 Jun 2;143(21):8177-8183. doi: 10.1021/jacs.1c03243. Epub 2021 May 19.
As with bulk ices, two-dimensional (2D) ices exhibit diverse crystalline structures, and the majority of these 2D structures have been predicted based on classical molecular dynamics (MD) simulations. Here, the spontaneous freezing transition of 2D liquid water within hydrophobic nanoslits is demonstrated for the first time using first-principles MD simulations. Various 2D ices are observed under different lateral pressure and temperature conditions. Notably, the liquid water confined to a 6.0 Å-wide nanoslit can spontaneously freeze into a monolayer ice consisting of an array of zigzag water chains at 2.5 GPa and 250 K. Moreover, within an 8.0 Å-wide nanoslit and at 4.0 GPa and 300 K, a previously unreported bilayer ice forms spontaneously that has a structure resembling that of the double surface layers of bulk ice-VII. Both 2D crystalline ices do not obey the ice rule, suggesting first-principles simulation can access a certain phase space that is not easily approached using classical simulations.
与块状冰一样，二维（2D）冰也呈现出多样的晶体结构，并且这些二维结构中的大多数都是基于经典分子动力学（MD）模拟预测出来的。在此，首次利用第一性原理分子动力学模拟证明了疏水纳米狭缝内二维液态水的自发冻结转变。在不同的侧向压力和温度条件下观察到了各种二维冰。值得注意的是，限制在6.0 Å宽的纳米狭缝中的液态水在2.5 GPa和250 K时可自发冻结成由锯齿形水链阵列组成的单层冰。此外，在8.0 Å宽的纳米狭缝内以及4.0 GPa和300 K时，会自发形成一种先前未报道过的双层冰，其结构类似于块状冰-VII的双表面层结构。这两种二维晶体冰均不遵循冰规则，这表明第一性原理模拟能够进入某些经典模拟不易触及的相空间。
